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EP-2016-314

(Submitted on 07 Jan 2017)

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Abstract

Using proton-proton collision data corresponding to an integrated luminosity
of 3.0 fb$^{-1}$, recorded by the LHCb detector at centre-of-mass energies of 7
and 8 TeV, the $B_{c}^{+} \rightarrow D^{0} K^{+}$ decay is observed with a
statistical significance of 5.1 standard deviations.
By normalising to $B^{+} \rightarrow \bar{D}^{0} \pi^{+}$ decays, a
measurement of the branching fraction multiplied by the production rates for
$B_{c}^{+}$ relative to $B^{+}$ mesons in the LHCb acceptance is obtained, $$
R_{D^{0} K} = \frac{f_{c}}{f_{u}}\times\mathcal{B}(B_{c}^{+} \rightarrow D^{0}
K^{+}) = (9.3\,^{+2.8}_{-2.5} \pm 0.6) \times 10^{-7}\,, $$ where the first
uncertainty is statistical and the second is systematic. This decay is expected
to proceed predominantly through weak annihilation and penguin amplitudes, and
is the first $B_{c}^{+}$ decay of this nature to be observed.

Figures and captions

Tree (a), penguin (b), and weak annihilation (c) diagrams for the decays studied. In each case, the meson appearing before the comma denotes the favoured decay.

Supplementary material for LHCb-PAPER-2016-058
Contains the invariant mass fits to the B- -> (D0 -> K- π+) π- and B- -> (D0 -> K- π+ π- π+) π- modes, in Fig. 1 and Fig. 2, respectively. The normalisation yield used in this paper is taken from the sum of the signal yields measured in both of these fits.